Technology advances in microchips, batteries, and various other small scale and high power applications are increasingly constrained by the need for effective thermal management. For example, increasing the speed of microprocessors may depend on effective new thermal management techniques to dissipate high heat fluxes. Similarly, electronic actuators that may take the place of hydraulics and mechanical actuators in aircraft may require similarly effective thermal management schemes. It is desirable that these thermal management, i.e., thermal transfer, schemes meet the criteria of low power consumption, low physical volume, and low weight owing to the small scale of many intended applications. Further, it is desirable that the heat transfer system should have few moving parts, require very little maintenance, and perform reliably in variable environmental conditions.
Phase change materials (PCM), i.e., materials that undergo a reversible latent energy transition upon transfer of thermal energy thereto, and particularly discrete particles of micro-encapsulated phase change material (MEPCM), have been proposed as a heat transfer material for microelectronics in stationary heat sink and heat pipe type heat transfer systems; such as in U.S. Pat. No. 5,007,478 and US Patent Application no. 2004/0159422, respectively. In these stationary heat sink and heat pipe type heat transfer systems flow conditions of the phase change material do not exist or are easily ignored.
In macro-scale heat transfer applications, MEPCM slurry, i.e., a two component fluid of liquid and suspended solids, has been suggested for use, such as in Colvin et al., U.S. Pat. No. 4,911,232. In these macro-scale systems, flow conditions of the slurry are basically laminar. Due to the large scale of such applications, there is no apparent concern for weight, volume or power consumption constraints.
In some microelectronic heat transfer systems, microchannel heat exchangers incorporating finned-microchannels have been suggested to achieve high cooling coefficients through high convective heat transfer coefficients and extended cooling surface area, such as in Goodson et al., US Patent Application no. 2003/0062149. However, due to flow condition considerations for the thermal transfer media, i.e., coolant fluid, within the microchannels, only liquid-component phase change materials of the boiling type have been suggested for use with microchannels.